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What Are Probiotics?

Probiotics are living microorganisms that can have health benefits when you consume them in high enough amounts. These can be bacteria or yeast that are similar to helpful organisms found naturally in your body, especially in the digestive tract. You can find them in some fermented foods, like yogurt. Probiotics also have become popular supplements and food additives, most often used to promote healthy digestion.


Probiotics vs. Prebiotics

Probiotics are different from prebiotics. Prebiotics are food ingredients that make it through your digestive tract intact and provide food for the helpful bacteria in your colon. These foods are high in fiber or certain kinds of starch. Foods high in prebiotics include oatmeal, bananas, berries, asparagus, and beans. You can also buy prebiotic supplements. Prebiotics and probiotics are sometimes combined in products called synbiotics.

Types of Probiotics

There are many probiotic organisms found in foods and supplements. They include:

  • Lactobacilli (like Lactobacillus acidophilus and Lactobacillus GG)
  • Bifidobacteria (like Bifidobacterium bifidus)
  • Yeasts (like Saccharomyces boulardii)

Different organisms have different effects. So while one may help with diarrhea or a vaginal infection, another may have no effect. Before you start taking a probiotic supplement, talk to your health care provider to make sure that you get the one most likely to help.

Probiotic Benefits

Probiotics change levels of microorganisms in the intestines, improving the overall mix, which is called your microbiome. When that mix is out of balance, doctors call it dysbiosis. Probiotics can treat dysbiosis by boosting the numbers of helpful bacteria and driving down the numbers of harmful bacteria. 

In general, probiotics might:

  • Help maintain your microbiome or get it back in balance after it's disturbed
  • Produce helpful substances in your body
  • Influence your immune responses

Although research is ongoing, there's good evidence that some probiotics may be help treat:

  • Irritable bowel syndrome
  • Some types of diarrhea
  • Colitis (particularly ulcerative colitis and and a complication of surgery for ulcerative colitis called pouchitis)
  • Acne
  • Eczema in children

They may also be used to help prevent diarrhea when you take antibiotics.

In addition, researchers are studying probiotics to see if they help with:

  • Certain types of stomach ulcers (those caused by H. pylori)
  • Infections (including urinary tract, vaginal, sinus, gastrointestinal, and respiratory bugs)
  • Dental disease
  • Allergies
  • Liver diseases 

But more research is needed to know if probiotics are safe and effective for these conditions.

Some researchers also believe a healthy microbiome affects:

  • Mental health
  • Mental sharpness
  • Pain tolerance
  • Inflammation
  • Blood sugar
  • Fat storage

Probiotics and Weight Loss 

There's reason to think probiotics might help with weight loss, because the microbes in your gut play an important role in breaking down what you eat and turning food into energy. The theory is that a healthy microbiome helps you burn more calories and store less fat. Studies have found that the gut microbes of obese people differ from those of thinner people.

But studies of probiotics for weight loss have produced mixed results. In some of the studies, people consuming probiotics have lost more weight and body fat than those not consuming them; in others, there's been no difference. A couple of studies even found more weight gain in those getting probiotics.

The studies used different methods and different kinds of probiotics, so they're hard to compare.

When to Take Probiotics

Many people consume probiotics as part of their regular diets. If you eat yogurt with live, active cultures, or regularly sip kefir or fresh kombucha, you're probably getting some probiotics (though how many survive the trip through your digestive system varies). But if you're thinking of adding a lot of probiotics to your diet or taking supplements, it's a good idea to check with your doctor.

In some cases, your doctor may suggest probiotics to you. You might get them to:

  • Prevent infections, if you have a history of them
  • Restore your gut microbes after treatment with antibiotics or an illness that throws your microbiome out of balance

You might also want to try regular probiotic use if you have gut health issues and have noticed that probiotic foods or supplements help. 

Probiotic Dosage

Because there are so many different probiotic organisms, in so many supplements and foods, there is no set dosage. Ask your doctor for advice.

Some probiotic products are labeled with the number of live organisms they contain. These are called colony forming units (CFUs). Total microorganisms also might be listed by weight, but that can include both live and dead organisms, so isn't very useful. 

Many supplements contain 1 billion to 10 billion CFUs per dose, and some contain much higher numbers. In general, higher counts don't guarantee a product is more helpful. You can increase the chances that you're getting what's listed by looking for labels that show numbers expected at the end of the product's shelf life and by using products before they expire.




Probiotic Foods

Probiotics occur naturally in some fermented foods and are added to others. Keep in mind, though, that food processing often destroys many of these microbes, and the numbers that make it to your gut are sometimes small. Look for "live, active cultures," and a list of specific microorganisms on food labels. Not all microorganisms in fermented foods have proven benefits.

The advantage of getting probiotics from foods is that you'll probably get a broader mix of helpful organisms than you get in supplements. Also, some foods contain fiber, which can act as prebiotics and feed the helpful microbes in your gut.

Foods that might contain probiotics include:

  • Yogurt, made from milk or nondairy substitutes
  • Kefir, a fermented milk drink
  • Sauerkraut, fermented cabbage
  • Kimchi, fermented vegetables
  • Tempeh, a fermented soybean food often used as a meat substitute
  • Miso, a fermented soybean paste
  • Soy drinks, including some soy milks
  • Cottage cheese, which is curdled milk
  • Kombucha, a fermented drink made from tea, sugar, bacteria, and yeast 
  • Pickles and pickle juice (brined in water, not vinegar) 

Something to consider: Pasteurization, which is a heat treatment to kill potentially harmful bacteria, can affect probiotic levels in food. In the United States, commercial yogurt must be made from pasteurized milk. Probiotic cultures are added after that step, but some manufacturers add a heat step that kills those cultures, so they don't contain any live organisms. That's why it's important to read labels.

If you buy commercially packaged pickles, sauerkraut, or similar foods, those are typically pasteurized as well, and have no added bacteria. You can get live cultures by making the foods yourself or buying fresh versions from farmers' markets, delis, or other outlets.

Signs That Probiotics Are Working

If you are taking probiotics to help with a specific problem, you can often tell if they're helping. For example, if you have irritable bowel syndrome with diarrhea, constipation, or both, you should notice your poop becoming more regular. You might also have less gas and bloating.

If you are taking probiotics for general wellness or to boost your immune system, it might be harder to tell if they make any difference. If you're having fewer colds, for example, that could be for a lot of reasons.

Side Effects of Probiotics

Probiotics are generally safe but can come with some side effects and risks.

Side effects. Some may cause intestinal gas and bloating, especially when you first start using them. This is most likely if you have a sensitive gut or take large doses. Side effects often improve over time. If you think probiotics are causing them, try decreasing the dose or using the probiotics every other day until your tolerance builds.

Interactions. If you have any medical problems or take any medicines regularly, talk to your doctor before you start using probiotics. They could affect medicines such as antibiotics or immunosuppressive drugs.

Risks. If you have intestinal disease or damage, HIV, cancer, a weakened immune system, or excessive bacteria in your intestines, don't use probiotics without checking first with your doctor.



Probiotics are bacteria and yeasts that can have health benefits if you consume them in large enough amounts and they survive digestion. While there's good evidence they help with digestive problems and some other health issues, more study is needed to show their full effects. You can get probiotics in foods and supplements, but it's always a good idea to talk to your doctor before taking supplements or making a major diet change.

Probiotics FAQs

Is it good to take probiotics daily?

To get the most out of probiotics, it is best to consume them every day. Probiotics don't live forever, so you need to keep replacing your supply.

What food is highest in probiotics?

There's no single best choice. While yogurt is popular for its versatility and wide availability and is backed by quite a few studies, other foods with live, active cultures can be high in probiotics as well. But there's less research showing the microorganisms in some foods have benefits. Those include kimchi, kombucha, sauerkraut, miso, and pickles.

Who needs probiotics most?

Research has yet to show who is most likely to benefit from adding probiotic foods or taking supplements. Doctors are most likely to suggest them if you have a digestive problem or if you've had an illness or taken medications, such as antibiotics, that might upset your microbiome.



Show Sources

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